gecko/toolkit/content/widgets/videocontrols.css

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

.scrubber, .volumeControl {
    -moz-binding: url("chrome://global/content/bindings/videocontrols.xml#suppressChangeEvent");
}

.scrubber .scale-thumb {
    -moz-binding: url("chrome://global/content/bindings/videocontrols.xml#timeThumb");
}

.playButton, .muteButton,
.scrubber .scale-slider, .volumeControl .scale-slider {
    -moz-user-focus: none;
}

.mediaControlsFrame {
    direction: ltr;
}

/* CSS Transitions
 *
 * These are overriden by the default theme; the rules here just 
 * provide a fallback to drive the required transitionend event
 * (in case a 3rd party theme does not provide transitions).
 */
.controlBar:not([immediate]) {
    -moz-transition-property: opacity;
    -moz-transition-duration: 1ms;
}
.controlBar[fadeout] {
    opacity: 0.0;
}
.volumeStack:not([immediate]) {
    -moz-transition-property: opacity, margin-top;
    -moz-transition-duration: 1ms, 1ms;
}
.volumeStack[fadeout] {
    opacity: 0.0;
    margin-top: 0px;
}
.statusOverlay:not([immediate]) {
    -moz-transition-property: opacity;
    -moz-transition-duration: 1ms;
    -moz-transition-delay: 750ms;
}
.statusOverlay[fadeout] {
    opacity: 0.0;
}